[Activity of Krebs cycle oxidative enzymes in the brain in hypothermia]

Cooling of rats down to the rectal temperature of 33--35 degrees without the use of narcotic and neuroplegic drugs did not cause distinct alterations in activity of the oxidative enzymes of tricarboxylic acid cycle--isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, malate-, succinate- and pyruvate dehydrogenases in brain tissue. At the same time, inhibition of the activity of these dehydrogenases occurred in profound hypothermia (cooling to 19--20 degrees). In this case the activity of succinate dehydrogenase was decreased less distinctly as compared with the activity of NAD-dependent dehydrogenases. Succinic acid appears to be an especially important substrate for oxidation in brain of the chilled rats.